Complex industrial environments typically contain numerous organic vapors and a range of relative humidities. It is not possible to experimentally determine respirator breakthrough performance for every possible combination of vapor mixtures. A fundamental understanding of the physicochemical interaction of adsorption of vapor mixtures is needed is needed in order to properly model activated carbon bed behavior. Data generated by this proposal will be used to evaluate and modify existing respirator service-life models. The purpose of these investigations is to evaluate adsorption of organic vapor mixtures onto activated carbon. Experiments are designed to evaluate adsorption equilibria and kinetics. Binary vapor mixtures containing a variety of different polarities and functional groups at three different humidities will evaluated. The data will be analyzed using parameters of the Dubinin equilibrium model and the Wheeler kinetic model. These parameters include, equilibrium adsorption affinity coefficients and capacities and kinetic rate constants and capacities. Adsorption studies using silica gel are also proposed. Adsorption onto silica gel, a polar adsorbent, will help to determine the role of polar forces in adsorption and to evaluate the suitability of silica gel as an adsorbent. Successful completion of this project will provide a more fundamental understanding of adsorption of complex organic vapor mixtures onto activated carbon and silica gel.